Global warming could shorten day, report predicts
May 04,2007 00:00 by Bend_Weekly_News_Sources

Earth’s fa­mil­iar 24-hour day may be­come about 12 hundred-thou­sandths of a sec­ond shorter due to the long-term trend of glob­al warm­ing, a new re­port con­tends.

Along­side var­i­ous en­vi­ron­men­tal dis­as­ters that sci­ent­ist pre­dict will en­sue from glob­al warm­ing—believed to be caused by emis­sions of heat-trapping gas­es due to hu­man ac­tiv­i­ties—another ef­fect would be a re­dis­tri­bu­tion of Earth’s wa­ter. This would oc­cur be­cause of changes in wa­ter tem­per­a­tures.

Fe­lix W. Lan­derer of the Max Planck In­sti­tute for Me­te­or­ol­ogy in Ham­burg, Ger­ma­ny, and col­leagues cal­cu­lat­ed the ef­fects of this re­dis­tri­bu­tion on the Earth’s spin. This in turn de­ter­mines the length of the day.

If an ap­pre­ci­a­ble amount of the weight of ocean wa­ters re­dis­tributes it­self to­ward the poles, this re­duces the ex­tent to which the plan­et as a whole bulges at the equa­tor. This then re­sults in some­thing si­m­i­lar to what hap­pens when a spin­ning skat­er pulls her arms in to­ward her­self: the spin speeds up.

Earth may witness an analogous effect, Lan­derer and col­leagues re­ported in a pa­per pub­lished March 28 in the jour­nal Geo­phys­i­cal Re­search Let­ters. The ef­fect oc­curs be­cause a rise in ocean tem­per­a­tures would raise sea lev­els, the sci­ent­ists ex­plained. A con­si­der­able amount of ocean mass may trans­fer away from deep wa­ters to shal­lower con­ti­nen­tal shelves, the sea­beds that surround con­ti­nents.

In ad­di­tion, “the con­ti­nen­tal con­fig­u­ra­tion is such that there is a lot of shelf ar­ea es­pe­cial­ly in the high­er north­ern lat­i­tudes,” near the North pole, Lan­derer wrote in an e­mail. Thus, a move­ment to­ward shelf ar­e­as means a move­ment to­ward Earth’s ax­is of ro­ta­tion, and away from the equa­tor.

By the end of the next cen­tu­ry, enough wa­ter mass could shift to short­en the length of day by about 0.12 thou­sandths of a sec­ond, Lan­derer’s team pre­dicted. They based their cal­cu­la­tions on fu­ture ocean con­di­tions pre­dicted by the In­ter­gov­ern­men­tal Pan­el on Cli­mate Change Fourth As­sess­ment.